Electronic transaction processing systems may utilize a payment terminal. The payment terminal can process payment transactions and interact with payment devices such as a payment card having a magnetic strip that is swiped in a magnetic reader of the payment terminal, a payment device having a Europay/Mastercard/Visa (EMV) chip that is inserted into a corresponding EMV slot of the payment terminal, and near field communication (NFC) enabled devices such as a smart phone or EMV card that is tapped at the payment terminal and transmits payment information over a secure wireless connection.
Electronic devices such as electronic cards may store information that may be used for communications and processing of transactions. For example, EMV cards may have an EMV chip located on the EMV card. The EMV card may not have its own power and clock source, and may receive its power and clock signal from another device such as a payment terminal. The EMV chip may interface with a device such as the payment terminal or a portion thereof, which may provide a clock source for the EMV chip, e.g., by connecting clock, power and ground pins of the EMV chip to a clock source, power source, and ground of the payment terminal. Once the EMV chip is connected to a power source, it may communicate with the payment reader or terminal via one or more data lines at a rate determined by clock rate of the clock source. In this manner, the EMV chip may exchange information as required to complete a transaction such as a payment transaction.
The EMV chip and payment reader or terminal may begin exchanging messages after power is applied to the EMV chip. A speed at which information such as encrypted payment information may be exchanged depends on the clock rate of the clock source signal. In the case of payment transactions, exchanging the requisite number of messages between EMV chip and payment reader or terminal for performing transaction processing may take a number of clock cycles to complete. During this time, the EMV chip and the payment terminal must remain connected in order to maintain the power, clock, and data connections.